import type { Vec2, Mat3 } from '../types';
import { estimateHomography, applyHomography } from '../geometry/homography';

/** Per-point reprojection error in pixels: |H·machine − image|. */
export function residuals(H: Mat3, machine: Vec2[], image: Vec2[]): number[] {
  if (machine.length !== image.length) throw new Error('residuals: machine/image length mismatch');
  return machine.map((m, i) => {
    const p = applyHomography(H, m);
    return Math.hypot(p[0] - image[i]![0], p[1] - image[i]![1]);
  });
}

interface CalibPoint {
  machine: Vec2;
  image: Vec2;
}

export interface CalibrationDeps {
  panel: HTMLElement;
  overlay: HTMLCanvasElement;
  onHomography: (H: Mat3, points: CalibPoint[]) => void;
}

/**
 * Renders the calibration panel. Flow: enter machine X/Y → click "Click point in video" →
 * click the spindle tip in the video → repeat ≥4× → "Compute".
 *
 * Captured image points and the resulting homography are in normalized [0,1] camera-frame
 * coordinates (machine-mm → normalized image), so they are display-size independent.
 * The JSON output structure stays the same (imagePoints now hold normalized values).
 */
export function mountCalibration(deps: CalibrationDeps): void {
  const { panel, overlay } = deps;
  const points: CalibPoint[] = [];
  let pendingMachine: Vec2 | null = null;

  panel.innerHTML = `
    <h2>Calibration</h2>
    <div class="row"><small>Jog the spindle to a known X/Y, enter it, then click the tip in the video.</small></div>
    <div class="row">
      X <input id="cal-x" type="number" step="0.1" />
      Y <input id="cal-y" type="number" step="0.1" />
      <button id="cal-arm">Click point in video</button>
    </div>
    <ul id="cal-list"></ul>
    <div class="row">
      <button id="cal-compute">Compute homography</button>
      <button id="cal-clear">Clear</button>
    </div>
    <textarea id="cal-json" rows="6" style="width:100%" readonly placeholder="Calibration JSON appears here"></textarea>
  `;

  const xEl = panel.querySelector('#cal-x') as HTMLInputElement;
  const yEl = panel.querySelector('#cal-y') as HTMLInputElement;
  const armBtn = panel.querySelector('#cal-arm') as HTMLButtonElement;
  const list = panel.querySelector('#cal-list') as HTMLUListElement;
  const jsonEl = panel.querySelector('#cal-json') as HTMLTextAreaElement;

  const renderList = (errs?: number[]) => {
    list.innerHTML = points
      .map((p, i) => `<li>(${p.machine[0]}, ${p.machine[1]}) → img(${p.image[0].toFixed(3)}, ${p.image[1].toFixed(3)})${errs ? ` <small>err ${errs[i]!.toFixed(1)}px</small>` : ''}</li>`)
      .join('');
  };

  armBtn.addEventListener('click', () => {
    pendingMachine = [parseFloat(xEl.value), parseFloat(yEl.value)];
    if (Number.isNaN(pendingMachine[0]) || Number.isNaN(pendingMachine[1])) {
      pendingMachine = null;
      return;
    }
    overlay.classList.add('interactive');
  });

  overlay.addEventListener('click', (ev) => {
    if (!pendingMachine || !overlay.classList.contains('interactive')) return;
    const rect = overlay.getBoundingClientRect();
    // Store normalized [0,1] image coords (fraction of the displayed camera frame).
    // This makes the calibration independent of display/canvas size.
    const px: Vec2 = [
      (ev.clientX - rect.left) / rect.width,
      (ev.clientY - rect.top) / rect.height,
    ];
    points.push({ machine: pendingMachine, image: px });
    pendingMachine = null;
    overlay.classList.remove('interactive');
    renderList();
  });

  (panel.querySelector('#cal-clear') as HTMLButtonElement).addEventListener('click', () => {
    points.length = 0;
    jsonEl.value = '';
    renderList();
  });

  (panel.querySelector('#cal-compute') as HTMLButtonElement).addEventListener('click', () => {
    if (points.length < 4) {
      jsonEl.value = 'Need at least 4 points.';
      return;
    }
    const machine = points.map((p) => p.machine);
    const image = points.map((p) => p.image);
    const H = estimateHomography(machine, image);
    // Per-axis pixel residual (normalized error scaled by canvas width/height) — used only for misclick display.
    const errsPx = machine.map((m, i) => {
      const p = applyHomography(H, m);
      return Math.hypot((p[0] - image[i]![0]) * overlay.width, (p[1] - image[i]![1]) * overlay.height);
    });
    renderList(errsPx);
    jsonEl.value = JSON.stringify(
      { imagePoints: image, machinePoints: machine, homography: H },
      null,
      2,
    );
    deps.onHomography(H, [...points]);
  });
}